hello folks
i am about to implement some mods on the master section of my mixer which could simplify a lot my routing and patching, which are posted below.
I wish to avoid any issues about stage mismatching and signal degradation, so i would like to get your advice about it.
Actually I would like to avoid any active stages if this would be possible since all i/O are line sources/sinks.
thank you in advance
i am about to implement some mods on the master section of my mixer which could simplify a lot my routing and patching, which are posted below.
I wish to avoid any issues about stage mismatching and signal degradation, so i would like to get your advice about it.
Actually I would like to avoid any active stages if this would be possible since all i/O are line sources/sinks.
thank you in advance
Attachments
maybe my first entry was a bit too cryptic.
The first mod regards the add of an insert loop on the master section then an auxiliary input by passive mixing via shunt resistors.
In the second passive mixing is done to perform mono monitoring then an aux input on just monitoring section is added as well.
Anyone ?
The first mod regards the add of an insert loop on the master section then an auxiliary input by passive mixing via shunt resistors.
In the second passive mixing is done to perform mono monitoring then an aux input on just monitoring section is added as well.
Anyone ?
Thank you for your support
"active mono switch" differs since it is a seperate output while my purpose is to have all monitors (speakers + headphone) on mono at a fingertip by switch action.
Do those summing resistor put me on troubles (notable distortions etc..) ?
.. right now i am heading to unmod master bus since it is devoted to recording
"active mono switch" differs since it is a seperate output while my purpose is to have all monitors (speakers + headphone) on mono at a fingertip by switch action.
Do those summing resistor put me on troubles (notable distortions etc..) ?
.. right now i am heading to unmod master bus since it is devoted to recording
Attachments
Resistors are in general very linear at audio frequencies. Carbon comp have some thermal noise, but those are hard to buy any more. Metal film have less thermal noise.
Main limitation is the cable length of the additional cable. NJM2068 is a very quiet op amp, but rated at 2k ohm load. It doesn't take a lot of cable to get the capacitance up to <2k @ 20 khz. And the driver already has a 5.1k ohm load on it, the feedback resistor. An additional unity gain buffer driving your extra cable would eliminate the possibility that your highs would disappear. 4 m of RCA plug coax cable at 110 pf a foot is 1.3 uf. 1/2*pi*f*C at 20 khz is 4.2 ohms. twisted pair is about 4 times lower in pf per foot. So don't use RCA cable for mastering.
Only buffer I have a datasheet for is the LME49600 but I've never used one. Make sure your power supply has the additional milliamps to drive the buffer, and its load the cable. If your signal is only guitars and voice, no tinkly bells or top octave piano, I wouldn't worry about it.
Last edited:
I didnt really get all details or your answer, however i would strickly ask you if this design could stress those NJM4560 too much or if would be ok. On the proposed EXT IN I plan to run my soundcard output for monitoring (1m cable), summing resistor are 2.2k.
thank you
Attachments
NJM4560 is a fairly high current op amp. Typical voltage swing on +-15 supplies is 12 vac @ 120 ohms load. 1 m RCA cable has 330 pf capacitance or 17 ohms at 20 khz. 1 m twisted pair cable @ 75 pf would be about 75 ohms @ 20 khz. You didn't state how long your stereo cables are or which type. If your loads respond to 2 vac as full volume your signal might be alright, still contain a few highs.
BTW the TI LME49600 buffer is surface mount, which I find a PIT* since I don't have eagle solfware on a Windows PC for PCB layout nor a $10000 wave soldering machine. Linear Tech LT1010 buffer is a TO220 package that can be screwed to a heat sink by mere diy people.
BTW the TI LME49600 buffer is surface mount, which I find a PIT* since I don't have eagle solfware on a Windows PC for PCB layout nor a $10000 wave soldering machine. Linear Tech LT1010 buffer is a TO220 package that can be screwed to a heat sink by mere diy people.
Last edited:
imho the njm4560 can drive a 2k load with low distortion (see datasheet). a 2,2k res in series with the output should be no problem.
(the 10k res parallel to the output can be increased to 22k or so, less load, but not essential)
but you will get some signal attenuation with these res........
(the 10k res parallel to the output can be increased to 22k or so, less load, but not essential)
but you will get some signal attenuation with these res........
Attachments
Last edited: